MSPD as sample preparation method for determination of selected pesticide residues in apples

A method for extraction and fast gas chromatographic (GC) determination of twenty pesticide residues of different volatility and polarity at ultratrace concentration level in apples is presented. Apples as representatives of non-fatty food were chosen as a matrix; they are also a common raw material for baby food production. Under fast GC conditions employing a mass spectrometric detector (MSD), several parameters of the MSPD procedure were optimised. Samples were homogenised with sorbent Florisil, pesticides were eluted with the optimised volume of etylacetate. After solvent evaporation to dryness, reconstitution of the rest to toluene follow and the final extract was injected. Recoveries obtained at three selected concentration levels were determined. The optimised procedure led to recoveries ≥ 90 % for the majority of the studied pesticides and the limits of quantification (LOQs) < 5 μg.kg^-1. Repeatability of gas chromatography-mass spectrometry (GC-MS) measurements of the matrix matched standards, expressed as the relative standard deviation (RSD [%]), was in most cases acceptable for ultratrace concentration levels of pesticide residues.